LSU All-American cornerback Tyrann Mathieu, a Heisman Trophy finalist last season, has been dismissed from the team for a violation of team and university rules.

LSU coach Les Miles announced the dismissal at a Friday afternoon press conference, saying Mathieu—who was suspended for a game last year for reportedly failing a drug test—broke a “longstanding rule.”

“I think he’s a quality, quality guy who had behavioral issues,” Miles said of Mathieu.

Mathieu tweeted on late Friday, "So grateful for LSU & it's fans!! I wish those guys the best on their National title run... I'll be you guys biggest fan. Jeremiah 29:11"

The Times-Picayune of New Orleans, citing an unidentified person close to the player, reported that Mathieu failed another drug test. Several high-ranking LSU administrators said they either did not know which rule Mathieu had violated or refused to discuss the matter. School policy allows for a player to lose his scholarship even without another positive test if he does not fulfill all the terms of university probation.

"Being an athlete is a privilege," LSU athletic director Joe Alleva said. "It's a privilege and you have to follow the rules to take advantage of that privilege. And unfortunately, he doesn't have that privilege here anymore.

"He really is a good kid. It's a shame. But I told him this morning that he has the rest of his life and his life is still ahead of him. He still has a tremendous opportunity to do good things and I encouraged him to do those good things, and I think he will."

Alleva said the violation did not involve law enforcement and that the university had been trying to help Mathieu work through some unspecified issues.

"He's had help," Alleva said. "And we've been trying to help him all along in everything. We do everything we can to help these kids."

LSU, Sporting News' preseason No. 1 pick for the past two years, went through a similar distraction during last year’s fall camp, when starting quarterback Jordan Jefferson was arrested for his involvement in a bar fight. Jefferson missed nearly the first half of the season, and the Tigers didn’t lose a game.

Just last week, Miles indicated the staff was still deciding where to play Mathieu—at cornerback or nickelback. That means the staff has gained more confidence in redshirt freshman cornerback Jalen Collins, who 2011 All-American cornerback Morris Claiborne said last year was the best athlete on the team—even though he was redshirting.

With Mathieu gone, senior Tharold Simon—a top backup in 2011 who was suspended one game with Mathieu and tailback Spencer Ware last for reportedly testing positive for synthetic marijuana—and Collins likely start the season at cornerback.

The bigger impact in the loss of Mathieu is the LSU return game, where Mathieu could turn field position—and game momentum (see: Arkansas, Georgia games)—with punt returns. Those duties now likely fall to wideouts Odell Beckham Jr. and Jarvis Landry.

Mathieu has two years of eligibility remaining, but Miles indicated if Mathieu wants to play this season, it would have to be at a "lower level," indicating a drop from FBS to FCS, otherwise known as Division I-AA. NCAA transfer rules dictate that if a player wants to transfer to another FBS school, he has to sit out a year.

Mathieu won the Bednarik Award as national defensive player of the year last season and made several big plays at cornerback and on special teams, scoring four touchdowns (two on punt returns and two on fumble returns) intercepting two passes, causing six fumbles and recovering four.